A systematic reviewand meta-analysis included 26 observational studies (11 cohort studies, 14 secondary analyses of cessation interventions, 1 RCT) in healthy and clinical populations. The aim was to investigate change in mental health after smoking cessation compared with continuing to smoke assessing mental health with questionnaires designed to measure anxiety, depression, mixed anxiety and depression, psychological quality of life, positive affect, and stress. Follow-up mental health scores were measured between 7 weeks and 9 years after baseline. The median age was 44 (on average 48% men) and on average, participants smoked 20 cigarettes a day and scored 5.4 on the Fagerström test for nicotine dependence. The median length of follow up was 6 months. In 18 studies abstinence was biologically verified. In 7 studies participants received a psychological intervention as part of the cessation intervention. In 17 studies participants were motivated to quit. Anxiety significantly decreased between baseline and follow-up in quitters compared with continuing smokers (the standardised mean difference (SMD) −0.37 ;95% CI −0.70 to −0.03; 4 trials; I²=71%; P<0.03), so did depression (SMD −0.25;−0.37 to −0.12; 10 trials; I²=30%; P<0.001), mixed anxiety and depression (−0.31; −0.47 to −0.14; 5 trials, I²=0%; P<0.001), and stress (–0.27; −0.40 to −0.13; 3 trials; I²=0%; P<0.001). Both psychological quality of life and positive affect significantly increased between baseline and follow-up in quitters compared with continuing smokers 0.22 (0.09 to 0.36; 8 trials; I²=63%; P<0.001) and 0.40 (0.09 to 0.71; 3 trials;, I²=49%; P<0.01), respectively. There was no evidence that the effect size differed between the general population and populations with physical or psychiatric disorders.
Date of latest search: 20 February 2014